1. Field of the Invention
The present invention generally relates to the field of bone implants and more particularly to spinal implants. Spinal implant embodiments may stabilize and/or fuse together vertebrae. Some spinal implant embodiments may be inserted during a posterior lumbar interbody fusion procedure.
2. Description of Related Art
An intervertebral disc may degenerate. Degeneration may be caused by trauma, disease, and/or aging. An intervertebral disc that becomes degenerated may have to be partially or fully removed from a spinal column. Partial or full removal of an intervertebral disc may destabilize the spinal column. Destabilization of a spinal column may result in alteration of a natural separation distance between adjacent vertebrae. Maintaining the natural separation between vertebrae may prevent pressure from being applied to nerves that pass between vertebral bodies. Excessive pressure applied to the nerves may cause pain and/or nerve damage. During a spinal fixation procedure, a spinal implant may be inserted within a space created by the removal or partial removal of an intervertebral disc between adjacent vertebrae. The spinal implant may maintain the height of the spine and restore stability to the spine. Bone growth may fuse the implant to adjacent vertebrae.
A spinal implant may be inserted during a spinal fixation procedure using an anterior, lateral, or posterior spinal approach. A discectomy may be performed to remove or partially remove a defective or damaged intervertebral disc. The discectomy creates a disc space for a spinal implant. The amount of removed disc material may correspond to the size and type of spinal implant to be inserted.
Spinal surgery may be complex due in part to the proximity of the spinal cord and/or the cauda equina. Preparation instruments and spinal implants may need to be carefully inserted to avoid damage to nerve tissue. Alignment and spacing of a spinal implant that is to be inserted into a patient may be determined before surgery. Achieving the predetermined alignment and spacing during surgery may be important to achieve optimal fusion of adjacent vertebrae.
Bone graft and/or bone implants may be used to promote bone growth that will fuse vertebrae together. Bone graft may be autogenic bone, allogenic bone, synthetic material, xenogenic bone or combinations thereof. Autogenic bone is bone obtained from another location of a patient. Allogenic bone is bone derived from the same species as the patient. Xenogenic bone is bone derived from a species other than that of the patient. Implants may be formed of metal, polymers, ceramics, autogenic bone, allogenic bone, xenogenic bone, or combinations thereof
U.S. Pat. No. 5,814,084 to Grivas et al., which is incorporated by reference as if fully set forth herein, describes diaphysial cortical bone dowels. The dowels are obtained from transverse plugs across the diaphysis of long, bones. The natural intramedullary canal of the source bone may form a cavity through the dowel perpendicular to the length of the dowel.
U.S. Pat. No. 6,025,538 to Yaccarino, III, which is incorporated by reference as if fully set forth herein, describes a composite allograft bone device. A first bone component is formed with a plurality of grooves. A second bone component is formed with a plurality of protrusions that mate with the grooves of the first bone component. A pin positioned at an oblique angle through the bone components joins the components together to form the composite allograft bone device.
U.S. Pat. No. 6,143,033 to Paul et al., which is incorporated by reference as if fully set forth herein, describes an allogenic intervertebral implant. The intervertebral implant is an annular plug that conforms in size and shape to end plates of adjacent vertebrae. Top and bottom surfaces of the implant have teeth to resist expulsion and to provide initial stability.